Tris[6-(dimethylamino)-1-azulenyl]methyl Hexafluorophosphate

Shunji Ito,* Shigeru Kikuchi, Noboru Morita, and Toyonobu Asao. Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-857...
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J. Org. Chem. 1999, 64, 5815-5821

5815

Tris[6-(dimethylamino)-1-azulenyl]methyl Hexafluorophosphate. Extremely Stable Methyl Cation with the Highest pKR+ Value Shunji Ito,* Shigeru Kikuchi, Noboru Morita, and Toyonobu Asao Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan Received January 5, 1999

Extremely stable carbocations, tris[6-(dimethylamino)- and 6-morpholino-1-azulenyl]methyl (2e and 2f), bis[6-(dimethylamino)-1-azulenyl][4-(dimethylamino)phenyl]methyl (3e), and [6-(dimethylamino)-1-azulenyl]bis[4-(dimethylamino)phenyl]methyl (4e) cations, were prepared, and their properties were fully characterized. These cations showed extremely high stabilities with high pKR+ values. The values of 2e and 3e were determined spectrophotometrically in DMSO/water as 24.3 ( 0.3 and 21.5 ( 0.2, respectively, which are higher than those of tri(1-azulenyl)methyl and di(1-azulenyl)phenylmethyl cations (2a and 3a) by 13.0 and 11.0 pK units. The value of 4e was determined to be 14.0 ( 0.1 in 50% aqueous acetonitrile and 14.3 ( 0.2 in DMSO/water, which is higher than that of (1-azulenyl)diphenylmethyl cation (4a) by 11.0-11.3 pK units. The extreme stability of these methyl cations is attributable to the dipolar structure of the azulene rings, in addition to the contribution of the mesomeric effect of three dimethylamino groups. The electrochemical reduction of 2e, 3e, and 4e showed a wave at -1.26, -1.22, and -1.14 V (V vs Ag/Ag+), respectively, upon cyclic voltammetry (CV). The relatively high reduction potentials, compared with those of unsubstituted parent 1-azulenylmethyl cations (2a, -0.78; 3a, -0.66; and 4a, -0.48 V), also exhibited the electrochemical stabilization of these methyl cations by the dimethylamino substituents. The oxidation of 2e, 3e, and 4e exhibited an irreversible, barely separated two-step, one-electron oxidation wave to generate a trication species at a potential range of 0.50-0.75 V upon CV. Introduction Recently, we have reported the synthesis of a series of azulene analogues of triphenylmethyl cation (1), i.e., tri(1-azulenyl)methyl, di(1-azulenyl)phenylmethyl, and (1-azulenyl)diphenylmethyl hexafluorophosphates (2a‚ PF6-, 3a‚PF6-, and 4a‚PF6-) and their derivatives (e.g., 2b,c‚PF6-, 3b,c‚PF6-, and 4b,c‚PF6-) (Chart 1).1 These cations (2a-c, 3a-c, and 4a-c) showed extreme stabilities with high pKR+ values (e.g., 2a, 11.3; 3a, 10.5; and 4a, 3.0). tert-Butyl substituents on each azulene ring effectively stabilized these cations by their steric effect and also by their inductive electronic effects induced by the C-C hyperconjugations with the π systems, although the inductive electronic effect of the methyl substituent was small. The value (14.3) of 2c is the highest for a methyl cation substituted with only hydrocarbon groups ever reported and is 3.0 pK units higher than that of 2a and 20.7 pK units higher than that of 1 (pKR+ -6.4).2 In our continuing efforts to prepare extremely stable carbocations, we have investigated the introduction of three methoxy substituents on both the azulenyl and phenyl rings of 1-azulenylmethyl cations (2a, 3a, and 4a), i.e., tris(6-methoxy-1-azulenyl)methyl, bis(6-methoxy-1azulenyl)(4-methoxyphenyl)methyl, and (6-methoxy-1azulenyl)bis(4-methoxyphenyl)methyl hexafluorophos(1) (a) Ito, S.; Morita, N.; Asao, T. Tetrahedron Lett. 1991, 32, 773. (b) Ito, S.; Morita, N.; Asao, T. Tetrahedron Lett. 1994, 35, 751. (c) Ito, S.; Morita, N.; Asao, T. Tetrahedron Lett. 1994, 35, 3723. (d) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1995, 68, 1409. (e) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1995, 68, 2011. (f) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1995, 68, 2639. (g) Ito, S.; Fujita, M.; Morita, N.; Asao, T. Chem. Lett. 1995, 475. (h) Ito, S.; Fujita, M.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1995, 68, 3611. (i) Ito, S.; Morita, N.; Asao, T. J. Org. Chem. 1996, 61, 5077. (2) Arnett, E. M.; Bushick, R. D. J. Am. Chem. Soc. 1964, 86, 1564.

phates (2d‚PF6-, 3d‚PF6-, and 4d‚PF6-) (Chart 1).3 The methoxy groups of 2d (pKR+ >14.0), 3d (pKR+ >14.0), and 4d (pKR+ 13.2) stabilized the parent 1-azulenylmethyl cations (2a, 3a, and 4a) by over 2.7, 3.5, and 10.2 pK units, respectively. Very recently, Lauresen et al. reported 2,6,10-tris(diethylamino)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium hexafluorophosphate as an extremely stable carbocation with the highest pKR+ value (19.7) for a carbonium ion.4 Triphenylmethyl cation is also effectively stabilized by dimethylamino substituents. The pKR+ value of tris[4-(dimethylamino)phenyl]methyl cation is 9.36,5 which is much higher than that of tris(4-methoxyphenyl)methyl cation (pKR+ 0.82).2 Amino substituents on both azulenyl and phenyl rings (2e, 3e, and 4e) are expected to stabilize the methyl cations (2a, 3a, and 4a) much more effectively. Our recent work on the higher stability of the cations 3f-h and 4f-h (pKR+ 13.2-13.8 and 12.5-13.3, respectively),6 compared with that of 3i-k and 4i-k (pKR+ 11.7-13.4 and 5.2-7.0, respectively),3b is also in agreement with this postulation. In this paper, we will report the synthesis and extreme stabilities of tris[6-(dimethylamino)- and 6-morpholino1-azulenyl]methyl hexafluorophosphates (2e,f‚PF6-), as well as the corresponding 4-(dimethylamino)phenyl analogues, i.e., bis[6-(dimethylamino)-1-azulenyl][4-(dimeth(3) (a) Ito, S.; Kikuchi, S.; Morita, N.; Asao, T. Chem. Lett. 1996, 175. (b) Ito, S.; Kikuchi, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1999, 72, 839. (4) Laursen, B. W.; Krebs, F. C.; Nielsen, M. F.; Bechgaard, K.; Christensen, J. B.; Harrit, N. J. Am. Chem. Soc. 1998, 120, 12255. (5) (a) Goldacre, R. J.; Phillips, J. N. J. Chem. Soc. 1949, 1724. (b) Deno, N. C.; Schriesheim, A. J. Am. Chem. Soc. 1955, 77, 3051. (6) Ito, S.; Kobayashi, H.; Kikuchi, S.; Morita, N.; Asao, T. Bull. Chem. Soc. Jpn. 1996, 69, 3225.

10.1021/jo990029p CCC: $18.00 © 1999 American Chemical Society Published on Web 07/21/1999

5816 J. Org. Chem., Vol. 64, No. 16, 1999 Chart 1

ylamino)phenyl]methyl and [6-(dimethylamino)-1-azulenyl]bis[4-(dimethylamino)phenyl]methyl hexafluorophosphates (3e‚PF6- and 4e‚PF6-), for comparison. Results and Discussion Synthesis. The successive sequence1,3,6 of the acidcatalyzed condensation of azulenes with aldehydes and hydride abstraction of the condensation products using DDQ could not be utilized for the synthesis of the salts 2e‚PF6- and 3e‚PF6-, although this sequence was effective for the synthesis of the salts 2a‚PF6- and 3a‚PF6-. Neither high- nor normal-pressure reaction of 6-(dimethylamino)azulene (5)7 with 6-(dimethylamino)-1-azulenecarbaldehyde (6), which was synthesized from 5 by Vilsmeier formylation in 91% yield, and 4-(dimethylamino)benzaldehyde (7) in the presence of acetic acid afforded the desired condensation products, tris[6-(dimethylamino)-1-azulenyl]methane and bis[6-(dimethylamino)1-azulenyl][4-(dimethylamino)phenyl]methane. However, we found that the tris(6-bromo-1-azulenyl)methyl and bis(6-bromo-1-azulenyl)[4-(dimethylamino)phenyl]methyl hexafluorophosphates (8‚PF6- and 9‚PF6-) could be readily replaced by the secondary amines to give the salts 2e‚PF6- and 3e‚PF6-. (7) 6-(Dimethylamino)azulene (5) was prepared in four steps starting from 4-pyrone in 25% yield according to the literature: (a) Zeller, K.-P. In Houben-Weyl Methoden der Organischen Chemie; Mu¨ller, E., Ed.; Georg Thiem Verlag: Stuttgart, 1985; Vol. 5, Part 2c, 127. (b) Bauer, W.; Mu¨ller-Westerhoff, U. Tetrahedron Lett. 1972, 1021.

Ito et al. Scheme 1

High pressure (10 kbar) was required for the reaction of 6-bromoazulene (10)8 with 6-bromo-1-azulenecarbaldehyde (11) to prepare tris(6-bromo-1-azulenyl)methane (12) as shown in Scheme 1. This condition was effective for the acid-catalyzed condensation of azulenes with relatively low reactive aldehydes.1c,1f,3,6 The high-pressure reaction of 10 with 11 in the presence of sodium acetate at 40 °C for 2 d in 50% acetic acid/dichloromethane afforded the desired 12 in 18% yield, together with 1,3bis[bis(6-bromo-1-azulenyl)methyl]azulene (13) (Chart 2) in 24% yield. Addition of the sodium acetate was essential for this reaction. Without addition of the base, the yield of 12 decreased considerably as a result of the decomposition of both products (12 and 13) and starting materials (10 and 11) in the reaction conditions. Hydride abstraction reaction of 12 with DDQ in dichloromethane at room temperature proceeded under similar conditions for the preparation of 2a.1,3,6 Addition of a 60% aqueous solution of HPF6 afforded the salt 8‚PF6- in quantitative yield. The reaction of 8‚PF6- with dimethylamine in acetonitrile at room temperature afforded the desired salt 2e‚PF6in 18% yield. Tris(6-morpholino-1-azulenyl)methyl hexafluorophosphate (2f‚PF6-) was also prepared by the similar treatment of 8‚PF6- with morpholine in 18% yield. Salt 3e‚PF6- was also synthesized in moderate yield by the similar reaction of bis(6-bromo-1-azulenyl)[4-(dimethylamino)phenyl]methyl hexafluorophosphate (9‚PF6-) with dimethylamine. High-pressure reaction (10 kbar) of 2 molar amounts of 10 with 7 at 40 °C for 1 d in the presence of sodium acetate in 50% acetic acid/dichloromethane afforded bis(6-bromo-1-azulenyl)[4-(dimethylamino)phenyl]methane (14) in 11% yield, together with a diastereomeric mixture of 1,3-bis{(6-bromo-1-azulenyl)[4-(dimethylamino)phenyl]methyl}-6-bromoazulene (15a and 15b) in 11% yield in a ratio of ca. 1:1. Compounds 15a and 15b were readily separable by silica gel column chromatography. Hydride abstraction reaction of 14 with DDQ in dichloromethane at room temperature followed by addition of a 60% aqueous solution of HPF6 yielded (8) McDonald, R. N.; Richmond, J. M.; Curtis, J. R.; Petty, H. E.; Hoskins, T. L. J. Org. Chem. 1976, 41, 1811.

Tris[6-(dimethylamino)-1-azulenyl]methyl PF6

J. Org. Chem., Vol. 64, No. 16, 1999 5817

Chart 2

Scheme 3

Table 1. Longest Wavelength Absorptions and Coefficients of 2e, 3e, and 4e and Those of 2a,d, 3a,d, and 4a,d, for Comparison1d,3

Scheme 2

9‚PF6- in 97% yield. The reaction of 9‚PF6- with dimethylamine in acetonitrile at room temperature afforded the salt 3e‚PF6- in 27% yield (Scheme 2). In contrast to the synthesis of 2e‚PF6- and 3e‚PF6-, salt 4e‚PF6- was prepared in high yield by the hydride abstraction of [4-(dimethylamino)-1-azulenyl]bis[4-(dimethylamino)phenyl]methane (16), which was obtained

sample

λmax, nm

log 

sample

λmax, nm

log 

2a 2d 2e 2f 3a

614 620 617 624 639

4.70 4.87 4.95 4.96 4.57

3d 3e 4a 4d 4e

624 614 487 535 594

4.83 4.88 4.16 4.34 4.92

by the similar acid-catalyzed condensation of 6-(dimethylamino)azulene (5) with 4,4′-bis(dimethylamino)benzhydrole (17) (Scheme 3). The reaction of 5 with 17 in acetic acid at room temperature for 10 min afforded the desired methane 16 in 61% yield, together with 1,3-bis{bis[4(dimethylamino)phenyl]methyl}azulene (18) in 54% yield. Hydride abstraction of 16 with DDQ in dichloromethane at room temperature followed by addition of a 60% aqueous solution of HPF6 afforded the salt 4e‚PF6- in 95% yield. Spectroscopic Properties. Mass spectra of 2e‚PF6-, 3e‚PF6-, and 4e‚PF6- ionized by FAB showed the correct M+ - PF6 ion peaks, which indicated the ionic structure of these compounds. The characteristic bands of hexafluorophosphate were observed at 845 (strong) and 558 (medium) cm-1 in their IR spectra, which also supported their ionic structure. These salts 2e‚PF6-, 3e‚PF6-, and 4e‚PF6- also showed strong absorption in visible region, as did the salts 2a‚PF6-, 3a‚PF6-, and 4a‚PF6-, and so on.1,3,6 Their absorption maxima (nm) and coefficients (log ) are summarized in Table 1. UV-vis spectra of 2e, 3e, and 4e in acetonitrile and those of the related unsubstituted and 6-methoxy analogues (2a,d, 3a,d, and 4a,d) are shown in Figures 1-3.1d,3b Although absorption maxima of tri(1-azulenyl)methyl cations (2a) were little influenced by the electron-donating substituents, cations 3e and 4e exhibited a hypsochromic shift of 25 nm and a bathochromic shift of 107 nm, respectively, compared with those of the parent unsubstituted cations 3a and 4a.1d The magnitude of the shifts by the dimethylamino substituents were much larger than those by methoxy substituents. The coefficient tends to increase upon substitution with dimethylamino, as well as with methoxy substituents. These results are in agreement with those of substituted triphenylmethyl cations. The longest

5818 J. Org. Chem., Vol. 64, No. 16, 1999

Ito et al. Table 2. pKR+ Values and Redox Potentialsa of 2e, 3e, and 4e and Those of 2a,d, 3a,d, and 4a,d, for Comparison1d,3

Figure 1. UV-vis spectra of cations 2e (solid line), 2a (broken line), and 2d (dotted line) in acetonitrile.

Figure 2. UV-vis spectra of cations 3e (solid line), 3a (broken line), and 3d (dotted line) in acetonitrile.

Figure 3. UV-vis spectra of cations 4e (solid line), 4a (broken line), and 4d (dotted line) in acetonitrile.

absorption maximum and coefficient of the triphenylmethyl cation (431 nm (log  4.60)) increase by substitution with electron-donating groups. Those of the tris(4dimethylaminophenyl)methyl and tris(4-methoxyphenyl)methyl cations are 621 (log  5.02) and 483 nm (log  5.02), respectively.9 In contrast to the high stabilities, the chemical shifts (13C NMR) of the cationic carbons for 2e, 3e, and 4e (156.44, 162.08, and 169.98 ppm, respectively) are almost comparable with those for 2a, 3a, and 4c (157.40, 165.54,

sample

pKR+

E1(red)

E2(red)

E1(ox)

E2(ox)

2e 3e 4e 2d 3d 4d 2a 3a 4a

24.3 ( 0.3 21.5 ( 0.2 14.0 ( 0.1 >14.0 >14.0 13.2 11.3 10.5 3.0

-1.26 -1.22 -1.14 -0.88 -0.80 -0.69 -0.78 -0.66 (-0.48)

(-1.92) (-1.89) (-1.84) (-1.64) (-1.63) (-1.62) (-1.56) (-1.52)

(+0.50) (+0.56) (+0.65) (+0.90) (+0.94) (+1.33) (+0.98) (+1.04) (+1.41)

(+0.64) (+0.63) (+0.75) (+0.98) (+1.07)

a The redox potentials were measured by cyclic voltammetry (V vs Ag/Ag+, 0.1 M Et4NClO4 in acetonitrile, Pt electrode, and scan rate 100 mV s-1). In the case of irreversible waves, which are shown in parentheses, Eox and Ered were calculated as Epa (anodic peak potential) -0.03 V and Epc (cathodic peak potential) +0.03 V, respectively.

and 168.58 ppm, respectively). However, the 13C NMR of cations 2e, 3e, and 4e exhibited considerable upfield shifts in the positions of C-2 (4.66-10.31 ppm), C-3a (9.74-13.64 ppm), C-5 (17.40-22.94 ppm), C-7 (18.5024.91 ppm), and C-8a (9.17-15.43 ppm) compared with 2a, 3a, and 4c.1d Salt 2f‚PF6- also showed spectroscopic properties similar to those of 2e‚PF6- (see Experimental Section). pKR+ Values and Redox Potentials. The pKR+ value of 4e was determined spectrophotometrically at 25 °C in a buffer solution prepared in 50% aqueous acetonitrile.10 The value of 4e determined in these conditions was 14.0 ( 0.1, which is higher than that of 4a by 11.0 pK units.1d The exact pKR+ values of cations 2e and 3e could not be determined by these conditions because of their high stabilities. Therefore the system of dimethyl sulfoxide (DMSO)/water/tetramethylammonium hydroxide (0.011 M) was used for the measurement.11 The H- scale (Hammet acidity scale) in the system ranges from 12 in water up to 26.2 in 99.6 mol % DMSO/water. The values of 2e and 3e could be determined in this system as 24.3 ( 0.3 and 21.5 ( 0.2, respectively. The value of 4e could also be determined in this system as 14.3 ( 0.2. The neutralization of cations 2e, 3e, and 4e was not completely reversible because of the instabilities of the neutralized products in the basic conditions. Acidification of the alkaline solution of 2e, 3e, and 4e with HCl regenerated the absorption maxima in the visible region by 32%, 57%, and 89%, respectively. The values of 2e and 3e are extremely high for a methyl cation. These values are higher than those of 2a and 3a by 13.0 and 11.0 pK units (Table 2).1d The extreme stability of these methyl cations is attributable to the dipolar structure of the azulene rings, in addition to the contribution of the mesomeric effect of three dimethylamino groups. The redox potentials (V vs Ag/Ag+) of 2e, 3e, and 4e measured by cyclic voltammetry (CV) in acetonitrile are also summarized in Table 2, together with those of the corresponding unsubstituted and 6-methoxy analogues (2a,d, 3a,d, and 4a,d).1d,3 The reduction of 2e, 3e, and 4e showed a reversible wave at -1.14 to -1.26 V and an (9) (a) Barker, C. C.; Bride, M. H.; Hallas, G.; Stamp, A. J. Chem. Soc. 1961, 1285. (b) Deno, N. C.; Jaruzelshi, J. J.; Schriesheim, A. J. Am. Chem. Soc. 1955, 77, 3044. (10) (a) Kerber, R. C.; Hsu, H. M. J. Am. Chem. Soc. 1973, 95, 3239. (b) Komatsu, K.; Masumoto, K.; Waki, Y.; Okamoto, K. Bull. Chem. Soc. Jpn. 1982, 55, 2470. (11) Dolman, D.; Stewart, R. Can. J. Chem. 1967, 45, 911.

Tris[6-(dimethylamino)-1-azulenyl]methyl PF6

irreversible wave at -1.84 to -1.92 V. The more negative reduction potentials of the dimethylamino derivatives (2e, 3e, and 4e), lower than those of 2a, 3a, and 4a by 0.48-0.66 V, correspond to their high electrochemical stabilities. The reduction of 2e also showed a small irreversible wave (-1.51 V) upon CV, just after the reversible wave and before the irreversible wave. The oxidation of 2e, 3e, and 4e exhibited voltammograms that were characterized by barely separated irreversible waves at 0.50-0.75 V due to the oxidation of two rings to generate a trication radical. The first oxidation potentials of 2e, 3e, and 4e are less positive than those of 2a,d, 3a,d, and 4a,d by 0.48-0.76 V. This behavior resembles the reported two-electron oxidation of 2,6,10-tris(diethylamino)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium hexafluorophosphate at 1.30 and 1.37 V vs SCE.4 In the oxidation of 2e, 3e, and 4e, another irreversible wave was observed at 1.27, 1.36, and 1.52 V, respectively, upon CV, after the irreversible two waves. As expected, these cations showed high stabilities with extremely high pKR+ values. These results indicate that the three dimethylamino substituents on both azulenyl and phenyl rings stabilized the methyl cations effectively. The pKR+ values of 3e and 4e were well beyond 20. To the best of our knowledge, the values of 3e and 4e are the highest ones for carbocations ever reported. This unusual stability of 2e, 3e, and 4e is ascribed to the dipolar structures of the azulene rings, in addition to the contribution of the mesomeric effect of the three dimethylamino groups.

Experimental Section General Procedures. Melting points were determined on a micro melting point apparatus and are uncorrected. Mass spectra were usually obtained at 70 eV. 1H NMR spectra (13C NMR spectra) were recorded at 90 (22.5), 400 (100), 500 (125), or 600 MHz (150 MHz). Voltammetry measurements were carried out with an electrochemical workstation equipped with Pt working and auxiliary electrodes and a reference electrode formed from Ag/AgNO3 (0.01 M) and tetraethylammonium perchlorate (TEAP) as a supporting electrolyte, at the scan rate of 100 mV s-1. Elemental analyses were performed at the Instrumental Analysis Center of Chemistry, Faculty of Science, Tohoku University. High-pressure reactions were carried out using a high-pressure apparatus purchased from Hikari-High Press Inc. Caution: Although there was no report of the explosion of the high-pressure apparatus, proper safty measures should be adopted when handling the high-pressure apparatus. 6-Bromo-1-azulenecarbaldehyde (11). POCl3 (2.2 mL, 24 mmol) was slowly added at 0 °C to a solution of 6-bromoazulene (10) (4.15 g, 20.0 mmol) in DMF (80 mL). The solution was stirred at room temperature for 30 min. The resulting solution was poured into ice-water, made alkaline with 2 M aqueous NaOH, and then extracted with CH2Cl2. The organic layer was washed with water, dried with MgSO4, and concentrated in vacuo. Purification of the residue by column chromatography on silica gel with CH2Cl2 gave the azulene 11 (4.39 g, 93%): violet plates; mp 86.0-87.0 °C; MS m/z (relative intensity) 234 (M+, 85); ES (CH2Cl2) λmax, nm (log ) 242 (4.13), 271 (3.88), 319 (4.74), 362 (3.82), 381 (3.88), 393 (3.86), 538 (2.70); 1H NMR (400 MHz, CDCl3) δ 10.35 (s, 1H), 9.27 (d, J ) 10.5 Hz, 1H), 8.27 (d, J ) 4.2 Hz, 1H), 8.19 (d, J ) 10.5 Hz, 1H), 7.92 (dd, J ) 10.5, 1.7 Hz, 1H), 7.82 (dd, J ) 10.5, 1.7 Hz, 1H), 7.35 (d, J ) 4.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 186.84 (d), 144.14 (s), 142.46 (d), 138.48 (s), 137.44 (s), 136.96 (d), 135.74 (d), 132.63 (d), 131.52 (d), 127.30 (s), 120.48 (d). Anal. Calcd for C11H7OBr: C, 56.20; H, 3.00. Found: C, 56.55; H, 3.14.

J. Org. Chem., Vol. 64, No. 16, 1999 5819 Tris(6-bromo-1-azulenyl)methane (12). A mixture of 6-bromoazulene (10) (1.04 g, 5.00 mmol), 6-bromo-1-azulenecarbaldehyde (11) (590 mg, 2.51 mmol), and sodium acetate (1.03 g, 1.26 mmol) was placed into a sealed Teflon vessel (9.1 mL) and the vessel was filled with 50% acetic acid solution of CH2Cl2. The mixture was left at 10 kbar (40 °C) for 24 h. The reaction mixture was diluted with CH2Cl2. The organic solution was washed with 5% aqueous NaHCO3 and water, dried with MgSO4, and concentrated in vacuo. The residue was purified by column chromatography on silica gel with CH2Cl2 and GPC with CHCl3 to afford the methane 12 (199 mg, 18%), 1,3-bis[bis(6-bromo-1-azulenyl)methyl]-6-bromoazulene (13) (290 mg, 24%), the recovered 10 (332 mg, 32%), and the recovered 11 (22 mg, 3.7%). 12: blue crystals; mp 236.0-239.0 °C dec; MS m/z (relative intensity) 628 (M+, 1.1); ES (CH2Cl2) λmax, nm (log ) 240 (4.55), 275 (4.93), 297 (5.04), 345 (4.27), 358 (4.28), 629 (3.88); 1H NMR (600 MHz, CDCl3) δ 7.974 (d, J ) 10.3 Hz, 3H), 7.899 (d, J ) 10.5 Hz, 3H), 7.432 (dd, J ) 10.3, 1.8 Hz, 3H), 7.348 (d, J ) 3.9 Hz, 3H), 7.291 (dd, J ) 10.5, 1.8 Hz, 3H), 7.259 (d, J ) 3.9 Hz, 3H), 7.198 (s, 1H); 13C NMR (150 MHz, CDCl3) δ 139.650 (s), 138.579 (d), 135.378 (s), 134.865 (d), 134.786 (s), 133.267 (s), 131.716 (d), 125.985 (d), 125.435 (d), 118.707 (d), 35.975 (d). Anal. Calcd for C31H19Br3: C, 58.99; H, 3.03. Found: C, 58.40; H, 3.33. 13: blue crystals; mp 232.5-235.0 °C dec; MS (FAB) m/z (relative intensity) 1050 (M+, 11); ES (CH2Cl2) λmax, nm (log ) 240 (4.74), 295 (5.29), 358 (4.45), 605 (3.18); 1H NMR (600 MHz, CDCl3) δ 7.901 (d, J ) 10.3 Hz, 4H), 7.867 (d, J ) 10.8 Hz, 2H), 7.739 (d, J ) 10.5 Hz, 4H), 7.395 (dd, J ) 10.3, 1.8 Hz, 4H), 7.193 (d, J ) 10.8 Hz, 2H), 7.171 (d, J ) 3.9 Hz, 4H), 7.163 (dd, J ) 10.5, 1.8 Hz, 4H), 7.144 (d, J ) 3.9 Hz, 4H), 7.081 (s, 2H), 6.935 (s, 1H); 13C NMR (150 MHz, CDCl3) δ 139.781 (d), 139.590 (s), 138.453 (d), 135.100 (s), 134.927 (s), 134.808 (d), 134.745 (s), 134.123 (s), 134.025 (s), 133.181 (s), 131.897 (d), 131.802 (d), 125.999 (d), 125.244 (d), 125.198 (d), 118.510 (d), 36.163 (d). Anal. Calcd for C52H31Br5: C, 59.18; H, 2.96. Found: C, 59.23; H, 3.42. Bis(6-bromo-1-azulenyl)[6-(dimethylamino)phenyl]methane (14). A teflon vessel (9.1 mL) was filled with 6-bromoazulene (10) (1.04 g, 5.02 mmol), 4-(dimethylamino)benzaldehyde (7) (382 mg, 2.56 mmol), sodium acetate (1.07 g, 13.0 mmol), and a 50% acetic acid solution of CH2Cl2. The mixture was left at 10 kbar (40 °C) for 24 h. The reaction mixture was diluted with CH2Cl2. The organic solution was washed with 5% aqueous NaHCO3 and water, dried with MgSO4, and concentrated in vacuo. The residue was purified by column chromatography on silica gel with 20% ethyl acetate/CH2Cl2 and GPC with CHCl3 to afford the methane 14 (94 mg, 11%), 1,3-bis{(6-bromo-1-azulenyl)[4-(dimethylamino)phenyl]methyl}-6-bromoazulene (15a and 15b) (95 mg, 11%), and the recovered 10 (409 mg, 39%). Compounds 15a (fr. 1, 32 mg, 3.6%) and 15b (fr. 2, 20 mg, 2.2%) were separable by column chromatography on silica gel with ethyl acetate/ CH2Cl2/hexane (2:5:5). 14: greenish blue crystals; mp 156.0-158.0 °C; MS m/z (relative intensity) 543 (M+, 51); ES (MeCN) λmax, nm (log ) 235 (3.26), 286 (3.73), 359 (2.75), 607 (4.05); 1H NMR (400 MHz, CDCl3) δ 7.94 (d, J ) 10.1 Hz, 2H), 7.91 (d, J ) 10.5 Hz, 2H), 7.45 (d, J ) 3.8 Hz, 2H), 7.39 (dd, J ) 10.1, 1.9 Hz, 2H), 7.29 (dd, J ) 10.5, 1.9 Hz, 2H), 7.26 (d, J ) 3.8 Hz, 2H), 6.97 (d, J ) 8.7 Hz, 2H), 6.63 (d, J ) 8.7 Hz, 2H), 6.55 (s, 1H), 2.89 (s, 6H); 13C NMR (100 MHz, CDCl3) δ 149.04 (s), 139.57 (s), 138.78 (d), 135.99 (s), 134.62 (d), 134.56 (s), 133.53 (s), 132.92 (s), 131.86 (d), 129.25 (d), 125.73 (d), 125.27 (d), 118.59 (d), 112.58 (d), 41.85 (d), 40.66 (q). Anal. Calcd for C29H23NBr2: C, 63.87; H, 4.25; N, 2.57. Found: C, 63.72; H, 4.53; N 2.65. 15a: green crystals; mp 219.0-224.0 °C dec; MS (FAB) m/z 880 (M+); ES (CH2Cl2) λmax, nm (log ) 289 (5.17), 359 (4.22), 610 (2.96); 1H NMR (600 MHz, CDCl3) δ 7.906 (d, J ) 10.8 Hz, 2H), 7.902 (d, J ) 10.3 Hz, 2H), 7.744 (d, J ) 10.5 Hz, 2H), 7.375 (dd, J ) 10.3, 1.8 Hz, 2H), 7.341 (d, J ) 3.9 Hz, 2H), 7.236 (dd, J ) 10.5, 1.8 Hz, 2H), 7.212 (d, J ) 10.8 Hz, 2H), 7.192 (d, J ) 3.9 Hz, 2H), 7.983 (s, 1H), 6.839 (d, J ) 8.7 Hz, 4H), 6.552 (d, J ) 8.7 Hz, 4H), 6.463 (s, 2H), 2.880 (s, 12H);

5820 J. Org. Chem., Vol. 64, No. 16, 1999 NMR (150 MHz, CDCl3) δ 148.968 (s), 140.094 (d), 139.617 (s), 138.829 (d), 135.970 (s), 134.700 (s), 134.593 (d), 134.404 (s and s), 134.352 (s), 133.566 (s), 132.521 (s), 132.204 (d), 131.725 (d), 129.188 (d), 125.633 (d), 125.041 (d), 124.875 (d), 118.490 (d), 112.518 (d), 41.833 (d), 40.694 (q). Anal. Calcd for C48H39N2Br3: C, 65.25; H, 4.45; N, 3.17. Found: C, 65.43; H, 4.72; N, 3.19. 15b: green crystals; mp 160.0-163.0 °C; MS (FAB) m/z (relative intensity) 880 (M+, 31); ES (CH2Cl2) λmax, nm (log ) 243 (4.64), 287 (5.16), 358 (4.22), 610 (2.95); 1H NMR (600 MHz, CDCl3) δ 7.890 (d, J ) 10.3 Hz, 2H), 7.872 (d, J ) 10.5 Hz, 2H), 7.742 (d, J ) 10.5 Hz, 2H), 7.373 (dd, J ) 10.3, 1.9 Hz, 2H), 7.306 (d, J ) 3.9 Hz, 2H), 7.194 (d, J ) 10.5 Hz, 2H), 7.175 (dd, J ) 10.5, 1.9 Hz, 2H), 7.169 (d, J ) 3.9 Hz, 2H), 7.124 (s, 1H), 6.904 (d, J ) 8.7 Hz, 4H), 6.332 (d, J ) 8.7 Hz, 4H), 6.467 (s, 2H), 2.889 (s, 12H); 13C NMR (150 MHz, CDCl3) δ 148.973 (s), 140.152 (d), 139.527 (s), 138.709 (d), 135.822 (s), 134.637 (s), 134.544 (d), 134.461 (s), 134.434 (s), 134.321 (s), 133.468 (s), 132.697 (s), 131.912 (d), 131.811 (d), 129.198 (d), 125.700 (d), 125.025 (d), 124.837 (d), 118.467 (d), 112.581 (d), 41.786 (d), 40.692 (q). Anal. Calcd for C48H39N2Br3: C, 65.25; H, 4.45; N, 3.17. Found: C, 65.22; H, 4.63; N, 3.16. [6-(Dimethylamino)-1-azulenyl]bis[4-(dimethylamino)phenyl]methane (16). A solution of 6-(dimethylamino)azulene (5) (343 mg, 2.00 mmol) and 4,4′-(dimethylamino)benzhydrole (17) (541 mg, 2.00 mmol) in glacial acetic acid (12 mL) and CH2Cl2 (12 mL) was stirred at room temperature for 10 min under an argon atmosphere. The solvent was removed in vacuo. The residue was diluted with CH2Cl2. The organic solution was washed with 5% aqueous NaHCO3 and water. The layer was dried with MgSO4 and concentrated in vacuo. The residue was purified by column chromatography on silica gel with ethyl acetate/CH2Cl2 to afford the methane 16 (378 mg, 61%), 1,3-bis{bis[4-(dimethylamino)phenyl]methyl}-6-(dimethylamino)azulene (18) (367 mg, 54%), and the recovered 5 (93 mg, 27%). 16: purple needles; mp 234.0-236.0 °C dec; MS m/z (relative intensity) 423 (M+, 100); ES (CH2Cl2) λmax, nm (log ) 265 (4.51), 336 (4.82), 404 (4.29), 504 (2.83); 1H NMR (90 MHz, CDCl3) δ 7.95 (d, J ) 11.2 Hz, 1H), 7.94 (d, J ) 11.2 Hz, 1H), 7.03 (d, J ) 8.8 Hz, 4H), 6.94 (s, 1H), 6.63 (d, J ) 8.8 Hz, 4H), 6.38 (dd, J ) 11.2, 2.4 Hz, 1H), 6.33 (dd, J ) 11.2, 2.4 Hz, 1H), 5.84 (s, 1H), 3.17 (s, 6H), 2.88 (s, 12H); 13C NMR (22.5 MHz, CDCl3) δ 157.83 (s), 148.62 (s), 136.15 (d), 134.72 (s), 134.05 (s), 133.53 (d), 133.25 (s), 129.96 (d), 129.63 (d), 128.16 (s), 116.15 (d), 112.55 (d), 106.85 (d), 106.70 (d), 48.03 (d), 41.85 (q), 40.87 (q). Anal. Calcd for C29H33N3: C, 82.23; H, 7.85; N, 9.92. Found: C, 82.24; H, 7.72; N, 9.91. 18: violet prisms; mp 229.0-231.5 °C dec; MS m/z (relative intensity) 675 (M+, 95); ES (CH2Cl2) λmax, nm (log ) 264 (4.77), 347 (4.90), 392 (4.07), 408 (4.11), 539 (2.88); 1H NMR (90 MHz, CDCl3) δ 7.87 (d, J ) 11.3 Hz, 2H), 6.99 (d, J ) 8.8 Hz, 8H), 6.76 (s, 1H), 6.60 (d, J ) 8.8 Hz, 8H), 6.22 (d, J ) 11.3 Hz, 2H), 5.80 (s, 2H), 3.10 (s, 6H), 2.87 (s, 24H); 13C NMR (22.5 MHz, CDCl3) δ 157.46 (s), 148.44 (s), 134.72 (s), 133.01 (d), 132.00 (s), 131.58 (d), 129.50 (d), 128.71 (s), 112.49 (d), 105.87 (d), 47.91 (d), 41.51 (q), 40.81 (q). Anal. Calcd for C46H53N5: C, 81.74; H, 7.90; N, 10.36. Found: C, 81.83; H, 8.02; N, 10.11. Tris(6-bromo-1-azulenyl)methyl Hexafluorophosphate (8‚PF6-). DDQ (272 mg, 1.20 mmol) was added at room temperature to a solution of tris(6-bromo-1-azulenyl)methane (12) (472 mg, 0.748 mmol) in CH2Cl2 (100 mL). After the solution was stirred at the same temperature for 5 min, 60% HPF6 (10 mL) was added. After an additional 5 min of stirring at room temperature, water was added to the mixture. The resulting suspension was filtered with suction. The organic layer was separated, dried with MgSO4, and concentrated under reduced pressure. The residue was dissolved in CH2Cl2 (5 mL) and added to ether (100 mL). The precipitated crystals were collected by filtration, washed with ether, and dried in vacuo to give the salt 8‚PF6- (580 mg, 100%): purple powder; mp 221.0-224.0 °C dec; MS (FAB) m/z 627 (M+ - PF6); ES (MeCN) λmax, nm (log ) 237 (4.77), 289 (4.67), 334 (4.56), 622 (4.75); 1H NMR (600 MHz, MeCN-d3, 63 °C) δ 8.612 (d, J ) 10.6 Hz, 3H), 8.232 (dd, J ) 10.6, 1.9 Hz, 3H), 7.983 (br d, J 13C

Ito et al. ) 4.4 Hz, 3H), 7.829 (d, J ) 4.4 Hz, 3H), 7.754 (dd, J ) 10.7, 1.9 Hz, 3H), 7.586 (d, J ) 10.7 Hz, 3H); 13C NMR (150 MHz, MeCN-d3, 63 °C) δ 158.610 (s), 150.459 (s), 146.810 (d), 144.876 (s), 140.012 (s), 139.094 (d), 137.064 (d), 136.178 (d), 135.307 (d), 134.750 (s), 125.852 (d). Anal. Calcd for C31H18Br3‚PF6: C, 48.03; H, 2.34. Found: C, 48.31; H, 2.60. Tris[6-(dimethylamino)-1-azulenyl]methyl Hexafluorophosphate (2e‚PF6-). A solution of dimethylamine (406 mg, 9.01 mmol) in acetonitrile (25 mL) was added to a solution of 8‚PF6- (234 mg, 0.302 mmol) in acetonitrile (50 mL). After the reaction mixture was stirred at 0 °C for 10 min, the mixture was concentrated in vacuo. After the residue was dissolved in CH2Cl2, a 60% HPF6 solution (3 mL) and water (30 mL) were added to the mixture. The organic layer was separated, washed with water, dried with MgSO4, and concentrated in vacuo. The residue was crystallized from CH2Cl2/ ether to give the salt 2e‚PF6- (37 mg, 18%): deep purple powder; mp 210.0-213.0 °C dec; MS (FAB) m/z 667 (M+) and 522 (M+ - PF6); ES (MeCN) λmax, nm (log ) 243 (4.53), 319 (4.60), 392 (4.81), 455 (4.08), 617 (4.95); 1H NMR (600 MHz, MeCN-d3, 63 °C) δ 8.218 (d, J ) 11.5 Hz, 3H), 7.376 (d, J ) 11.8 Hz, 3H), 7.211 (d, J ) 4.2 Hz, 3H), 7.185 (d, J ) 4.2 Hz, 3H), 7.011 (dd, J ) 11.5, 2.8 Hz, 3H), 6.430 (dd, J ) 11.8, 2.8 Hz, 3H), 3.273 (s, 18H); 13C NMR (150 MHz, MeCN-d3, 63 °C) δ 161.022 (s), 156.438 (s), 141.533 (s), 138.799 (d), 137.328 (d), 136.546 (s), 136.372 (d), 133.907 (s), 122.112 (d), 115.268 (d), 113.353 (d), 41.847 (q). Anal. Calcd for C37H36N3‚PF6‚1/2H2O: C, 65.67; H, 5.51; N, 6.21. Found: C, 65.84; H, 5.00; N, 5.89. Tris[6-(1-morpholino)-1-azulenyl]methyl Hexafluorophosphate (2f‚PF6-). A solution of morpholine (530 mg, 6.08 mmol) in acetonitrile (20 mL) was added to a solution of 8‚PF6(155 mg, 0.200 mmol) in acetonitrile (30 mL). After the reaction mixture was stirred at 0 °C for 10 min, the mixture was concentrated in vacuo. After the residue was dissolved in CH2Cl2, a 60% HPF6 solution (3 mL) and water (30 mL) were added to the mixture. The organic layer was separated, washed with water, dried with MgSO4, and concentrated in vacuo. The residue was crystallized from CHCl3 to give the salt 2f‚PF6(28 mg, 18%): deep purple powder; mp 223.0-224.0 °C; MS (FAB) m/z 793 (M+) and 648 (M+ - PF6); ES (MeCN) λmax, nm (log ) 244 (4.56), 324 (4.61), 397 (4.83), 459 (4.16), 624 (4.96); 1 H NMR (600 MHz, MeCN-d3, 63 °C) δ 8.318 (d, J ) 11.5 Hz, 3H), 7.450 (d, J ) 11.7 Hz, 3H), 7.324 (d, J ) 4.1 Hz, 3H), 7.300 (d, J ) 4.1 Hz, 3H), 7.215 (dd, J ) 11.5, 2.9 Hz, 3H), 6.694 (dd, J ) 11.7, 2.9 Hz, 3H), 3.835 (t, J ) 4.9 Hz, 12H), 3.695 (t, J ) 4.9 Hz, 12H); 13C NMR (150 MHz, MeCN-d3, 63 °C) δ 161.603 (s), 156.507 (s), 142.898 (s), 139.245 (d), 137.837 (s), 137.771 (d and d), 134.005 (s), 122.554 (d), 117.191 (d), 115.458 (d), 66.163 (t), 48.895 (t). Anal. Calcd for C43H42N3O3‚ PF6‚3/2H2O: C, 62.92; H, 5.53; N, 5.12. Found: C, 62.98; H, 5.22; N, 5.13. Bis(6-bromo-1-azulenyl)[4-(dimethylamino)phenyl]methyl Hexafluorophosphate (9‚PF6-). DDQ (87 mg, 0.38 mmol) was added at room temperature to a solution of bis(6bromo-1-azulenyl)[4-(dimethylamino)phenyl]methane (14) (165 mg, 0.303 mmol) in CH2Cl2 (30 mL). After the solution was stirred at the same temperature for 5 min, 60% HPF6 (3 mL) was added. After an additional 5 min of stirring at room temperature, water was added to the mixture. The resulting suspension was filtered with suction. The organic layer was separated, dried with MgSO4, and concentrated under reduced pressure. The residue was dissolved in CH2Cl2 (3 mL) and added to ether (50 mL). The precipitated crystals were collected by filtration, washed with ether, and dried in vacuo to give the salt 9‚PF6- (202 mg, 97%): purple crystals; mp 137.5140.0 °C; MS (FAB) m/z 542 (M+ - PF6); ES (MeCN) λmax, nm (log ) 235 (4.56), 286 (5.03), 346 (4.02), 359 (4.05), 607 (2.75), 659 (2.65); 1H NMR (600 MHz, MeCN-d3, 63 °C) δ 8.545 (d, J ) 10.3 Hz, 2H), 8.133 (d, J ) 10.3 Hz, 2H), 8.005 (d, J ) 3.2 Hz, 2H), 7.782 (d, J ) 3.2 Hz, 2H), 7.742 (d, J ) 10.0 Hz, 2H), 7.599 (d, J ) 10.0 Hz, 2H), 7.449 (d, J ) 8.2 Hz, 2H), 7.053 (d, J ) 8.2 Hz, 2H), 3.391 (s, 6H); 13C NMR (150 MHz, MeCN-d3, 63 °C) δ 164.042 (s), 157.551 (s), 148.663 (s), 145.985 (d), 143.929 (s), 141.408 (d), 139.090 (s), 138.596 (d), 136.664 (d), 134.522 (d), 133.676 (d), 133.288 (s), 129.280 (s), 124.444 (d),

Tris[6-(dimethylamino)-1-azulenyl]methyl PF6 114.422 (d), 40.709 (q). Anal. Calcd for C29H22NBr2‚PF6: C, 50.53; H, 3.22; N, 2.03. Found: C, 50.08; H, 3.19; N, 2.42. Bis[6-(dimethylamino)-1-azulenyl][6-(dimethylamino)phenyl]methyl Hexafluorophosphate (3e‚PF6-). A solution of dimethylamine (406 mg, 9.01 mmol) in acetonitrile (25 mL) was added to a solution of 9‚PF6- (207 mg, 0.300 mmol) in acetonitrile (50 mL). After the reaction mixture was stirred at 0 °C for 10 min, the mixture was concentrated in vacuo. After the residue was dissolved in CH2Cl2, a 60% solution of HPF6 (3 mL) and water (30 mL) were added to the mixture. The organic layer was separated, washed with water, dried with MgSO4, and concentrated in vacuo. The residue was crystallized from CH2Cl2/ether to give the salt 3e‚PF6- (51 mg, 27%): purple powder; mp 182.0-184.0 °C; MS (FAB) m/z 617 (M+) and 472 (M+ - PF6); ES (MeCN) λmax, nm (log ) 238 (4.44), 334 (4.57), 390 (4.63), 614 (4.88); 1H NMR (600 MHz, MeCN-d3, 63 °C) δ 8.237 (d, J ) 11.6 Hz, 2H), 7.416 (d, J ) 11.8 Hz, 2H), 7.364 (d, J ) 8.9 Hz, 2H), 7.241 (d, J ) 4.4 Hz, 2H), 7.210 (d, J ) 4.4 Hz, 2H), 7.112 (dd, J ) 11.6, 3.0 Hz, 2H), 6.990 (d, J ) 8.9 Hz, 2H), 6.588 (dd, J ) 11.8, 3.0 Hz, 2H), 3.309 (s, 12H), 3.219 (s, 6H); 13C NMR (150 MHz, MeCNd3, 63 °C) δ 162.08 (br s), 161.478 (s), 153.54 (br s), 142.882 (s), 138.991 (d), 137.868 (d), 137.771 (d), 137.581 (s), 136.331 (d), 133.576 (s), 130.91 (br s), 132.412 (d), 116.862 (d), 114.651 (d), 112.871 (d), 41.960 (q), 40.383 (q). Anal. Calcd for C33H34N3‚ PF6‚2H2O: C, 60.64; H, 5.86; N, 6.43. Found: C, 60.53; H, 5.29; N, 6.23. [6-(Dimethylamino)-1-azulenyl]bis[4-(dimethylamino)phenyl]methyl Hexafluorophosphate (4e‚PF6-). DDQ (137 mg, 0.604 mmol) was added at room temperature to a solution of [6-(dimethylamino)-1-azulenyl]bis[4-(dimethylamino)phenyl]methane (16) (212 mg, 0.500 mmol) in CH2Cl2 (50 mL). After the solution was stirred at the same temperature for 5 min, 60% HPF6 (5 mL) was added. After 5 min of stirring at room temperature, water (50 mL) was added to the mixture. The resulting suspension was filtered with suction. The organic layer was separated, dried with MgSO4, and concentrated under reduced pressure. The residue was dissolved in CH2Cl2 (5 mL) and added to ether (80 mL). The precipitated crystals were collected by filtration, washed with ether, and dried in vacuo to give the salt 4e‚PF6- (271 mg, 95%): deep purple

J. Org. Chem., Vol. 64, No. 16, 1999 5821 powder; mp 249.0-251.0 °C; MS (FAB) m/z 567 (M+) and 422 (M+ - PF6); ES (MeCN) λmax, nm (log ) 204 (4.65), 255 (4.40), 328 (4.43), 387 (4.40), 594 (4.92); 1H NMR (500 MHz, MeCNd3) δ 8.127 (d, J ) 11.9 Hz, 1H), 7.337 (d, J ) 11.9 Hz, 1H), 7.198 (br, 4H), 7.144 (d, J ) 4.9 Hz, 1H), 7.137 (dd, J ) 11.9, 3.1 Hz, 1H), 7.098 (d, J ) 4.9 Hz, 1H), 6.809 (d, J ) 8.9 Hz, 4H), 6.674 (dd, J ) 11.9, 3.1 Hz, 1H), 3.282 (s, 6H), 3.130 (s, 12H); 13C NMR (125 MHz, MeCN-d3) δ 169.977 (s), 162.389 (s), 155.536 (s), 145.430 (s), 139.841 (d), 139.404 (s), 139.380 (br d), 138.941 (d), 137.787 (d), 134.460 (s), 128.344 (s), 125.869 (d), 119.719 (d), 116.624 (d), 112.694 (d), 43.060 (q), 40.525 (q). Anal. Calcd for C29H32N3‚PF6: C, 61.37; H, 5.68; N, 7.40. Found: C, 61.08; H, 5.69; N, 7.57. pKR+ Values of 2e and 3e. Each 1 mL portion of stock solution, prepared by dissolving 2-3 mg of the salts 2e‚PF6and 3e‚PF6- in DMSO (20 mL), was pipetted out and added to a 0.11 M (1 mL) or 1.1 M (0.1 mL) aqueous solution of tetramethylammonium hydroxide and an appropriate amount of water. The solution was made up to 10 mL by adding DMSO. The H- value of the sample solution was calculated by the concentration (mol %) of DMSO in water. The concentration of cations 2e and 3e was determined spectrophotomerically. The observed absorbances at the specific absorption maxima of cations 2e and 3e were plotted against the H-value, giving classical titration curves whose midpoints were taken as the pKR+ values.

Acknowledgment. This work was partially supported by a Grant-in-Aid for Scientific Research on Priority Areas “Creation of Delocalization Electronic Systems” (10146204) from the Ministry of Education, Science, Sports and Culture, Japan. Supporting Information Available: 1H and 13C NMR spectra for all mentioned compounds (2e,f‚PF6-, 3e‚PF6-, 4e‚PF6-, 8‚PF6-, 9‚PF6-, 11-16, and 18) and the cyclic voltammograms of 2e‚PF6-, 3e‚PF6-, and 4e‚PF6-. This material is available free of charge via the Internet at http:// pubs.acs.org. JO990029P